1. Technical Field
Several aspects of the present invention relate to an asynchronous serial communication method and an asynchronous serial communication device.
2. Related Art
An asynchronous circuit has been known for about 50 years. An asynchronous state machine, a calculating machine and the like using delay elements have been developed. However, after the synchronous design method which uses the global clock signal to drive a circuit was introduced in the 1970s so many kinds of small-scale integrated (SSI) circuit and medium-scale integrated (MSI) circuit driven by the global clock signal were developed that the synchronous circuit design techniques became dominant, while the asynchronous circuit design techniques have disappeared in the industry.
Recently as the chip size increases as well as the number of transistors integrated in a chip, the heat concentration and clock skew problems caused by high-frequency clocking have become serious matters. The limitations of synchronous circuit design techniques have been realized especially with the deep-submicron technologies. JP-A-2005-020308 is an example of the related art. To solve the problems, the example discloses a serial communication method, with which it is enable to lower the electric power of clocking in a synchronous serial communication device. The penalty for reducing the power consumption is circuit cost at the receiver. Even after the synchronized clock is stopped by the transmitter, the sampling clock needs to be generated by the receiver. The sampling clock ironically can increase the power consumption at the receiver, again.
Such problems in a backdrop highlight the needs for the asynchronous circuit design techniques to realize robust low-power low-noise very-large-scale-integration circuits (VLSI). Since the asynchronous circuit is self-timed, it is excellent to adopt in order to solve the malfunction problem caused by variations in voltage and temperature as well as the clock skew problem. In addition, the asynchronous circuits have advantages of low electromagnetic emission as well as low power consumption over the synchronous counterparts.
Meanwhile, low-temperature poly-crystalline-silicon (LTPS) thin-film transistor (TFT) technology, which have been often used for liquid-crystal displays, are now ready to be used for realizing flexible VLSI devices. The asynchronous circuit design can be used to compensate variations in the characteristics of LTPS TFTs, to fix the self-heating problem that is specific to LTPS TFTs, and then to come up with robust or stably-operating devices.
Following the above-mentioned trend, various asynchronous circuits have been developed for various applications. However, since any conventional asynchronous communication method between asynchronous devices has pros and cons, no asynchronous communication method has established its position yet.
There are two communication methods using 4-phase handshaking protocol for asynchronous serial communication devices. One uses dual-rail encoding for data and the other uses bundled-data scheme. Disadvantages of the former are that three signal lines (two data lines and one control line) are required for 1-bit data communication, which means that an extra signal line is needed and that the circuit structure is complicated compared with synchronous communication methods. Disadvantages of the latter are that three signal lines (one data line and two control lines) are required for 1-bit that a communication and that the communication speed is deteriorated by a delay element.
An advantage of the present invention is to provide an asynchronous serial communication method with which the number of signal lines can be reduced while obtaining a high-speed communication to a certain extent and the size of the circuit can be reduced. Another advantage of the invention is to provide an asynchronous serial communication device thereof.
An asynchronous serial communication method according to a first aspect of the invention includes a sender transmitting a one bit of serial data by firstly making a signal transition on the data line, secondly putting the one bit of serial data on the data line after a predetermined time T1 yet before another predetermined time T1+T2, and a receiver receiving the one bit of serial data by firstly detecting the signal transition on the data line and secondly capturing the one bit of serial data after a predetermined tune T3 (where T3>T1+T2).
According to the first aspect, when a sender transmitting a one bit of serial data makes a signal transition on the data line, the receiver detects the signal transition on the data line and captures a one-bit data sent by the sender after a predetermined time. Even though each data bit is accompanied with a preceding signal transition, the overhead time can be so small that an impact on the bandwidth is negligible. Therefore, it is possible to perform an asynchronous serial communication at a high speed to a certain extent with two communication wires: a data wire and a acknowledge wire, without a control wire. According to this asynchronous serial communication method, no complicated signal processing is required so that it is possible to reduce the size of a circuit.
An asynchronous serial communication method according to a second aspect of the invention includes a sender transmitting a one bit of serial data by firstly changing a signal level of the data line from a default level to the opposite level and then putting the one bit of serial data on the data line after a predetermined time T1 yet before another predetermined time T1+T2, and a receiver receiving the one bit of serial data by firstly detecting the signal transition on the data line and secondly capturing the one bit of serial data after a predetermined time T3 (where T3>T1+T2).
In this way, it is possible to perform an asynchronous serial communication at a high-speed to a certain extent with two communication wires: a data wire and a acknowledge wire, without a control wire. According to this asynchronous serial communication method, the size of a circuit can be reduced.
An asynchronous serial communication device according to a third aspect of the invention includes a sender communication port transmitting a one bit of serial data by firstly making a signal transition on the data line, secondly putting the one bit of serial data on the data line after a predetermined time T1 yet before another predetermined time T1+T2, and a receiver communication port receiving the one bit of serial data by firstly detecting the signal transition on the data line and secondly capturing the one bit of serial data after a predetermined time T3 (where T3>T1+T2), wherein the sender communication port and the receiver communication port are coupled each other through a single data line.
According to the third aspect of the invention, it is possible to perform an asynchronous serial communication at a high-speed to a certain extent with two communication wires: a data wire and a acknowledge wire, without a control wire. According to this asynchronous serial communication method, the size of a circuit can be reduced.
An asynchronous serial communication device according to a forth aspect of the invention includes a sender communication port transmitting a one bit of serial data by firstly changing a signal level of the data line from a default level to the opposite level and then putting the one bit of serial data on the data line after a predetermined time T1 yet before another predetermined time T1+T2, and a receiver communication port receiving the one bit of serial data by firstly detecting the signal transition on the data line and secondly capturing the one bit of serial data after a predetermined time T3 (where T3>T1+T2), wherein the sender communication port and the receiver communication port are coupled each other through a single data wire.
According to the forth aspect of the invention, it is possible to perform an asynchronous serial communication at a high-speed to a certain extent with two communication wires: a data wire and a acknowledge wire, without a control wire, so that it is also possible to reduce the size of a circuit.
An asynchronous serial communication device according to a fifth aspect of the invention performs data transmission through a plurality of data wires and includes
a sender communication port transmitting a word of serial multi-bit data by firstly making a signal transition on a designated data line among the data lines, secondly putting a word of serial multi-bit data on the data lines after a predetermined time T1 yet before another predetermined time T1+T2;
a receiver communication port receiving a word of serial multi-bit data by firstly detecting the signal transition on the designated data line among the data lines and secondly capturing a word of serial multi-bit data on the data lines after a predetermined time T3 (where T3>T1+T2).
According to the fifth aspect of the invention, a plurality of data lines is provided so that the sender communication ports can send a multi-bit data and the receiver ports can receive the multi-bit data. Since only one data line is used for the communication according to the asynchronous serial communication method, the size of the circuit can be reduced.
An asynchronous serial communication device according to a sixth aspect of the invention performs data transmission through a plurality of data lines and includes
a a sender communication port transmitting a word of serial multi-bit data by firstly making a signal transition on a designated data line among the data lines, secondly putting a word of serial multi-bit data on the data lines after a predetermined time T1 yet before another predetermined time T1+T2;
a receiver communication port receiving a word of serial multi-bit data bay firstly detecting the signal transition on the designated data line among the data lines and secondly capturing a word of serial multi-bit data on the data lines after a predetermined time T3 (where T3>T1+T2).
According to the sixth aspect of the invention, a plurality of data lines is provided so that the sender communication ports can send a multi-bit data and the receiver ports can receive the multi-bit data. Since only one data line is used for the communication according to the asynchronous serial communication method, the size of the circuit can be reduced.
An asynchronous serial communication device according to a seventh aspect of the invention includes a sender communication port transmitting a one bit of serial data by firstly making a signal transition on the that a line, secondly putting the one bit of serial data on the data line after a predetermined time T1 yet before another predetermined time T1+T2.
An asynchronous serial communication device according to an eighth aspect of the invention includes a sender communication port transmitting a one bit of serial data by firstly changing a signal level of the data line from a default level to the opposite level and then putting the one bit; of serial data on the data line after a predetermined time T1 yet before another predetermined time T1+T2.
An asynchronous serial communication device according to a ninth aspect of the invention includes a receiver communication port receiving the one bit of serial data by firstly detecting the signal transition on the data line and secondly capturing the one bit of serial data after a predetermined time T3 (where T3>T1+
In this case, the sender communication port may includes a send signal level retainer retaining the signal level of the send signal that was sent last, an inverted-signal generator generating the opposite signal level to the signal level of the send signal that was sent last, an output control signal generator generating an output control signal that has a predetermined pulse duration from an inputted sender port write signal, and a selector selecting and outputting either the signal level of the send signal that was sent last or the opposite signal level depending on the output control signal.
In this way, a complicated signal processing is not necessary and it is possible to reduce the circuit size and the current consumption.
Furthermore, the receiver communication port may include a signal change detector outputting a detection signal if the signal change detector detects the signal level change, and a read signal generator generating a data read signal after a predetermined time period past if the read signal generator reads the detection signal from the signal change detectors
In this way, a complicated signal processing is not necessary and it is possible to reduce the circuit size and the current consumption.
Moreover, the asynchronous serial communication device may further include a central processing unit (CPU) controlling the sender communication port and the receiver communication port.
In this case, the CPU directly controls the sender communication port and the receiver communication port and performs the asynchronous serial communication method so that a dedicated glue-logic circuit is not necessary. Therefore it is possible to reduce the circuit size and the current consumption.
The asynchronous serial communication device may further include an optical output unit and an optical detector, and wherein the signal level is an intensity of light. In this way, it is possible to perform a long-distance communication.
In the above-described asynchronous serial communication device, the signal level may be a direction of electric current. In this way, it is possible to perform a long-distance communication.
According to this invention, the sender communication port may be coupled to a plurality of the receiver communication ports where a point-to-multipoint communication is performed.
In this way, an acknowledgement signal generated by a rendezvous circuit that synchronizes acknowledgement signals from a plurality of the receivers is input to the sender communication port.
In this way, the sender communication port can send the send data to a plurality of the receiver communication ports.
Moreover, the sender communication port may send a packet that includes a destination address, a broadcast flag and data, and the receiver communication port receives the packet.
In this way, the sender communication port can send the send data to the plurality of the receiver communication ports.
Furthermore, the receiver communication port may continue and complete the receiving operation only when an address of the receiver communication port matches the destination address or when the broadcast flag is on.
In this way, the receiver communication port confirms the destination address and the broadcast flag of the packet so that only a selected one among the plurality of the receiver communication ports can receive the packet.